Anti-stiction layer deposition

Abstract

To provide techniques for improving anti-stiction coatings.SOLUTION: An anti-stiction layer is formed from a first organosilane precursor. A second organosilane precursor is introduced around a workpiece with the anti-stiction layer. The second organosilane precursor is different from the first organosilane precursor. The second organosilane precursor is configured to eliminate defect sites and unreacted sites on the anti-stiction layer and on a surface of the workpiece that includes the anti-stiction layer.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] This disclosure relates to films used in semiconductor manufacturing, and more specifically, to end cap films used in semiconductor devices.

Background Art

[0002] In both integrated circuit (IC) device manufacturing and microelectromechanical system (MEMS) manufacturing, layers or coatings of materials deposited on a workpiece are used. In certain examples, those layers are removed after deposition on the workpiece, for example, after pattern transfer to the underlying layer when the layer is used as a patterning masking material. In other examples, those layers are deposited so as to function within the device or system and remain as part of the manufactured device. There are numerous methods for depositing thin film layers or coatings. In applications where wear on the coating is likely to occur due to fluid flow or mechanical contact on the substrate surface on which the coating layer exists, it is beneficial to chemically bond the coating directly to the substrate surface and to obtain specific surface characteristics by doing so through the reaction of the type and its surface.

[0003] Among the fields currently attracting attention in relation to layers and coatings chemically bonded to the workpiece surface, there is a combination of a mechanical system called a microelectromechanical system (MEMS) and an integrated circuit. Due to the fact that some of the electrical devices are on the nanometer scale, and the use of MEMS in applications such as bioscience where specific functionality is imparted to the surface by utilizing the type and characteristics of the coating on the substrate surface, the need to improve the method for controlling the formation of coatings or layers on the substrate surface has been increasing. Historically, coatings of these types were deposited in the liquid phase, resulting in device yield losses due to capillary forces and limitations in controlling film characteristics. Recently, vapor deposition has come to be used as an alternative to liquid phase processing to improve coating characteristics.

[0004] Among the things that have received particular attention are the anti-stiction layers and coatings necessary to achieve the high-reliability long-term performance of MEMS. Stiction (adhesion) of compliant micro-mechanical parts is one of the fundamental reliability problems, and it has been found to be difficult to overcome. So far, solution-based anti-stiction monolayers have been used. However, recently, due to capillary stiction, particulate problems, and deficiencies in the quality, scalability, and reproducibility of films produced by long wet processes, efforts have been underway to develop vapor deposition methods for anti-stiction coatings. Vacuum processing and vapor deposition of anti-stiction coatings, such as self-assembled monolayers (SAMs), have generally come to result in higher-quality films. Integrated vapor deposition processes (including those with surface plasma treatment within the same chamber) generally allow for better control of surface reactivity, while leaving less room for stiction between micro-mechanical parts during the addition of anti-stiction coatings.

[0005] Molecular vapor deposition (MVD) is a process technology for depositing ultra-thin films by vapor deposition at low temperature on a wide variety of workpieces, such as semiconductor wafers or MEMS. In this process, ultra-thin functionalized organic or inorganic films can be grown with higher yields and better cost efficiency than conventional liquid-phase deposition techniques. Such films can serve as lubricating, protective, hydrophobic, hydrophilic, biocompatible, or reactive coatings. In MEMS applications, for example, MVD films are commonly used as anti-stiction coatings, thereby improving device performance and extending the overall device life.

[0006] Conventional methods for forming anti-stiction coatings on silicon wafers include those that individually administer organosilane molecules as precursors and those that co-administer organosilane precursors and water. In the latter case, the water promotes the adsorption and polymerization of organosilane molecules. The anti-stiction coatings formed are usually SAM films.

[0007] Some anti-stiction coatings can be grown in multiple modes. Some polymerization processes generate a polydimethylsiloxane-like (PDMS-like) polymer that is terminated with hydroxyl groups. These hydroxyl groups are harmful for certain applications such as anti-stiction because their presence reduces the hydrophobicity of the coating and the exposed OH groups may promote stiction. Current anti-stiction films include perfluorodecyltrichlorosilane (FDTS) coatings and fluorooctatrichlorosilane (FOTS) coatings. However, these thin films contain fluorine and are undesirable due to environmental concerns.

Prior Art Documents

Patent Documents

[0008]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0009] Therefore, there is a need for a technical improvement to improve the anti-stiction coating.

Means for Solving the Problems

[0010] In a first embodiment, a deposition method is provided. A first layer is deposited on a workpiece. The first layer is formed of a first organosilane precursor and can serve as an anti-stiction layer. A second organosilane precursor is introduced around the workpiece with the first layer. The second organosilane precursor is different from the first organosilane precursor. The second organosilane precursor is configured to eliminate defect sites and unreacted sites on the surface of the workpiece having the first layer and on the first layer.

[0011] The first layer can be deposited using vapor deposition.

[0012] By this method, a second organosilane precursor can also be deposited on the first layer using vapor deposition.

[0013] The first organosilane precursor may be dimethyldichlorosilane or dimethyldiethoxysilane. In one example, the second organosilane precursor is N,N-dimethyltrimethylsilylamine or trimethylchlorosilane.

[0014] The first layer may be a self-assembled monolayer.

[0015] The workpiece may be silicon or aluminum oxide.

[0016] The defect sites can be hydroxyl groups.

[0017] By this method, a purge process using an inert gas can also be performed between the deposition of the first layer and the introduction of the second organosilane precursor.

[0018] The second organosilane precursor may have at least the same chain length as the first organosilane precursor.

[0019] In a second embodiment, a device is provided. This device has a workpiece, a first layer disposed on the workpiece, and a second layer disposed on the first layer. The first layer is formed of a first organosilane precursor and can be an anti-stiction layer. The second layer is formed of a second organosilane precursor. The second organosilane precursor is different from the first organosilane precursor. The second organosilane precursor is configured to eliminate defect sites and unreacted sites on the surface of the workpiece having the first layer and on the first layer.

[0020] The workpiece may be silicon or aluminum oxide.

[0021] The first organosilane precursor may be dimethyldichlorosilane or dimethyldiethoxysilane. In one example, the second organosilane precursor is N,N-dimethyltrimethylsilylamine or trimethylchlorosilane.

[0022] The first layer may be a self-assembled monolayer.

[0023] The second organosilane precursor may have at least the same chain length as the first organosilane precursor.

[0024] The defect sites can be hydroxyl groups.

[0025] The workpiece can be part of a MEMS device.

[0026] For a more complete understanding of the nature and objects of the present disclosure, reference should be made to the following accompanying drawings in conjunction with the detailed description set forth below.

Brief Description of the Drawings

[0027]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0028] The subject matter recited in the claims is described by specific embodiments, but other embodiments are also within the technical scope of this disclosure, including embodiments in which all of the benefits and features described herein are not provided. Various structural, logical, processing step, and electronic modifications can be made without departing from the technical scope of this disclosure. Thus, the technical scope of this disclosure is defined solely by reference to the appended claims.

[0029] According to the embodiments of the present disclosure, by eliminating defect sites, the anti-stiction properties of SAM and other anti-stiction coatings can be improved. In the embodiments of the present disclosure, a first layer is deposited on the workpiece. The first layer probably contains defect sites, such as hydroxyl groups. Then, a second layer capable of eliminating the defect sites is deposited on the first layer. And by introducing a second precursor and preferably reacting it with the defect sites, those defect sites are removed. That is, the defects in the thin layer formed by the first precursor are repaired. By using two different types of organosilane molecules, an improved anti-stiction coating can be formed.

[0030] A method is depicted in FIG. 1 by a series of cross-sectional views. In step A, a workpiece 100 is provided. The workpiece 100 can be a semiconductor wafer or a MEMS device. For example, the workpiece 100 may be silicon or aluminum oxide.

[0031] In step B, a first layer 101 is deposited on the workpiece 100. This deposition is performed using MVD, another vapor deposition technique, a liquid chemical process, or other deposition techniques. During the deposition, a first organosilane precursor 103 is used. The first organosilane precursor 103 can also be introduced around the workpiece 100 together with water. The deposition of the first layer can be performed at a temperature of 20°C to 150°C. As an example, the administration of the first organosilane precursor 103 can be at 0.5 to 2 Torr, and the administration of water can be at 0.5 to 4 Torr.

[0032] In one example, the first organosilane precursor 103 and water vapor are retained in the MVD chamber for about 1 to 60 minutes. For example, a period of about 15 minutes can be used. To obtain better film quality, multiple reaction cycles with the first organosilane precursor 103 may be required. In one example, 1 to 10 reaction cycles are performed.

[0033] MVD is a gas-phase reaction between a surface-reactive chemical substance and a corresponding receiving surface, such as that of the workpiece 100. A bifunctional silane with a reactive terminal at one end of its molecule can be used. The advantage of the gas-phase reaction over a comparable liquid-phase process lies in the control of moisture from the ambient environment, which often causes cross-polymerization of silanes and results in retained microparticles on the treatment surface. In many cases, precise control of the reactant and water content is possible by using a heated near-atmospheric-pressure vacuum chamber. In addition, since the coverage of the reactants is generally diffusion-limited, complex parts can be treated in the gas-phase process. By using MEMS sensors, problems such as stiction and other parasitic problems related to surface-to-surface interactions can be addressed. An example of an MVD system is shown in Patent Document 1, the entire content of which is incorporated herein by reference.

[0034] In step C, the workpiece 100 is shown together with the first layer 101 formed by the first organosilane precursor 103. The first layer 101 can be either a single layer or a multilayer. In one example, the first layer 101 is a self-assembled monolayer. In one example, the first layer 101 may be an anti-stiction layer. Defects, such as those containing hydroxyl groups, may exist on the first layer 101. Based on the crystal structure of SiO 2 the number of defects will be less than 13 per nm 2 There may also be other numbers or frequencies of defects.

[0035] Although specifically disclosed in relation to the hydroxyl group, other defects may be formed and addressed during the use of the embodiments disclosed in the present application. For example, the defect may be chlorine, and it may be sealed by an amine group and the reaction by-product may be HCl. Aldehyde may react with an amine and H 2 O may be a by-product. With the techniques disclosed in the present application, other OH groups and NH groups may form defects and they may react with each other.

[0036] The thickness of the resulting first layer 101 can be about 0.2 nm to 10 nm for a silicon workpiece and about 0.2 nm to 100 nm for an aluminum workpiece. In one example, the thickness of the resulting first layer 101 is about 1 nm.

[0037] In step D, a second organosilane precursor 104 is introduced around the workpiece 100 with the first layer 101. The second organosilane 104 may be deposited together with other species or deposited without other species. The second organosilane 104 may be the only species necessary to eliminate the defect sites. The second organosilane precursor 104 is different from the first organosilane precursor 103. For example, the second organosilane precursor 104 can be deposited on the workpiece 100 using MVD. The temperature during the deposition of the second organosilane precursor 104 may be set to 20°C to 150°C. The pressure during the deposition of the second organosilane precursor 104 may be set to 0.1 Torr to 5 Torr.

[0038] In one example, the second organosilane precursor 104 is injected into the MVD chamber and deposited thereon on the first layer 101. The reaction time can be about 30 seconds to 2 hours. For example, the reaction time may be about 15 minutes. The unreacted second organosilane precursor 104 may be discharged at the end of step D.

[0039] In step E, a second layer 102 formed of a second organosilane precursor 104 is formed on the first layer 101. The second organosilane precursor 104 is configured to be able to eliminate defect sites on the first layer 101. The second organosilane precursor 104 is different from the first organosilane precursor 103. The second organosilane precursor 104 repairs the first layer 101 to its original structure by reacting with hydroxyl groups. By the reaction between the silane functional groups in the second organosilane precursor 104 and the hydroxyl groups in the first layer 101, Si-O bonds can be formed on the surface of the first layer 101 and dimethylamine can be released, and they can be gradually discharged out of the chamber. Thereby, since the defect sites are eliminated, the resulting anti-stiction characteristics of the device are improved.

[0040] In addition to the defect sites on the first layer 101 being eliminated, the defect sites on the surface of the workpiece 100 can also be eliminated. The surface may be the same as the surface of the workpiece 100 having the first layer 101. For example, a part of the workpiece 100 may be exposed after the first layer 101 is formed.

[0041] The precursors for the first layer 101 are generally small, but these precursors can also be polymerized to form longer chains. If the molecular length is the same as or shorter than that of the first organosilane precursor 103, the second organosilane precursor 104 can penetrate into the first layer 101 to some extent. However, the second organosilane precursor 104 can also be made to have the same length as or longer than the first organosilane precursor 103. The length and reactivity of the second organosilane precursor 104 can be selected such that reactions with residual OH groups, unreacted sites or defect sites can occur.

[0042] Although depicted as a flat layer in FIG. 1 for simplicity, the second organosilane 104 is selectively adsorbed onto the defective sites on the first layer 101. If there are no defects on the first layer 101, the second layer 102 is not formed there. The total number of defects after the addition of the second organosilane precursor 104 will be significantly less than 13 per 1 nm 2 .

[0043] The second layer 102 can be formed from a monofunctional precursor. In the case of a monofunctional compound, there is a tendency that no additional defect sites are introduced by the second organosilane precursor 104. In contrast, in the case of a bifunctional or trifunctional chemical substance, additional OH groups may be generated during the film formation reaction. By the total etching with a monofunctional compound and the reaction therewith, any existing defect sites can be eliminated.

[0044] By appropriately configuring the reactivity, dosage, and size of the molecules of the second organosilane precursor 104, the degree of defect elimination can be optimized. The functional group can be directly related to the chemical reactivity. Generally, an aminosilane functional group is more reactive than a chlorosilane functional group and an alkoxysilane functional group. According to thermodynamics, the reactivity can also be increased by increasing the temperature and dosage. If the molecules of the second organosilane precursor 104 are of small size, it means that the molecules can enter the voids and pores of the first layer 101, which is a geometric effect.

[0045] In one example, the first organosilane precursor 103 is dimethyldichlorosilane (DDMS) or dimethyldiethoxysilane. Other examples of the first organosilane precursor 103 can be other vapor deposition polymers, such as bis(N,N-dimethylamino)dimethylsilane, dimethyldimethoxysilane, diethoxydimethylsilane, or 1,3-dichloro-1,1,3,3-tetramethyldisiloxane. Mixtures of these precursors can also be employed. The first organosilane precursor 103 can also be an organosilane monomer having two reactive functional groups and capable of forming a polymer chain by polymerization.

[0046] In one example, the second organosilane precursor 104 is N,N-dimethyltrimethylsilylamine (TMSDMA) or trimethylchlorosilane (TMCS). Other organosilanes such as N,N-diethyltrimethylsilylamine (TMSDEA), methoxytrimethylsilane (TMSOMe), ethoxytrimethylsilane (TMSOEt), trimethylsilyl trifluoromethanesulfonate (TMSOTf) or trimethylsilyl fluorosulfonate (TMSOFs) can also be used as the second organosilane precursor 104. Mixtures of these precursors can also be employed. By appropriately selecting the second organosilane precursor 104, specific reaction by-products such as HCl or dimethylamine can also be avoided. In one example, the second organosilane precursor 104 can be a monofunctional silane.

[0047] In one example, the second organosilane precursor 104 can have at least the same chain length as the first organosilane precursor 103.

[0048] In one example, a purge process is performed between the introduction of the first organosilane precursor 103 and the introduction of the second organosilane precursor 104, or between the cycles in which the first organosilane precursor 103 is introduced. An inert gas such as N 2 or Ar can be used. Thereby, unreacted precursor gas and reaction by-products are purged.

[0049] The resulting device has a workpiece 100, a first layer 101 and a second layer 102. The first layer 101 can be an anti-stiction layer. The second layer 102 can eliminate defect sites (e.g., hydroxyl groups) on the first layer 101. The first layer 101 and the second layer 102 can also be anti-stiction films.

[0050] According to one embodiment, the method of FIG. 1 can be used for MEMS anti-stiction films. The layers formed using the method of FIG. 1 can be beneficial because they are fluorine-free layers. Fluorine-containing substances are generally not desirable for environmental reasons.

[0051] This method will be further described in connection with FIGS. 2-3. FIG. 2 shows a PDMS-like polymer with hydroxyl groups. FIG. 3 shows the elimination of hydroxyl groups by the use of another organosilane molecule. The hydroxyl groups in FIG. 2 are unreacted sites. As shown in FIG. 3, the organosilane molecule reacts with the hydroxyl groups to eliminate defects.

[0052] Unreacted sites refer to all chemical groups that can react with organosilane precursors. In anti-stiction applications, most unreacted sites are OH groups. For example, all OH groups remaining on the surface can be unreacted sites. Among the OH groups originally present on the surface, those that still exist because they did not react with the first organosilane precursor can correspond to this.

[0053] Defect sites such as OH groups can be formed during the reaction of the first organosilane precursor. Defect sites are generated post facto during the addition of the first layer and initially do not exist on the specimen surface.

[0054] Stiction was measured experimentally using an atomic force microscope (AFM). The end-capped DDMS coating had unbonded hydroxyl groups that needed to be passivated. The TMSDMA molecule can react with the hydroxyl groups, thereby passivating the DDMS film. Stiction was simulated by placing a silicon AFM tip in contact with the MVD-coated surface, and the anti-stiction properties of the coating were measured.

[0055] AFM was performed in soft tapping mode and force volume mode. The scanning results for 1×1 μm were collected at a resolution of 512×512 pixels. An adhesion map of 16×16 points over a 50×50 μm area was collected. This TMSDMA end-capped DDMS coating exhibits lower adhesion than that of the DDMS-only coating, as shown in the table below.

[0056]

Table 1

[0057] Although the present disclosure has been described in connection with one or more specific embodiments, it will be understood that other embodiments of the present disclosure can be made without departing from the technical scope of the present disclosure. That is, the present disclosure is limited only by the appended claims and their reasonable interpretation.

Claims

1. 1. A deposition method comprising the steps of: depositing a first layer on the workpiece, the first layer being formed from a first organosilane precaster, the first layer being an anti-stiction layer; introducing a second organosilane precast around the workpiece with the first layer, the second organosilane precast being different from the first organosilane precast and configured to eliminate defect sites and unreacted sites on the surface of the workpiece with the first layer and on the first layer; Deposition method.

2. The method of claim 1 , wherein the first layer is deposited using vapor phase deposition.

3. 10. The method of claim 1 further comprising depositing the second organosilane precast over the first layer using vapor deposition.

4. 2. The method of claim 1, wherein the first organosilane precipitator is dimethyldichlorosilane or dimethyldiethoxysilane.

5. The method of claim 4, wherein the second organosilane precipitator is N,N-dimethyltrimethylsilylamine.

6. 5. The method of claim 4, wherein the second organosilane precipitator is trimethylchlorosilane.

7. 10. The method of claim 1, wherein the first layer is a self-assembled monolayer.

8. 10. The method of claim 1, wherein the workpiece is silicon or aluminum oxide.

9. 2. The method of claim 1, wherein the defect sites are hydroxyl groups.

10. 10. The method of claim 1, further comprising performing a purge process using an inert gas between the deposition of the first layer and the introduction of the second organosilane precast.

11. 2. The method of claim 1, wherein the second organosilane precast has at least the same chain length as the first organosilane precast.

12. A device, comprising: A workpiece is provided. a first layer disposed on the workpiece, the first layer being formed of a first organosilane precast and the first layer being an anti-stiction layer; a second layer disposed on the first layer, the second layer being formed of a second organosilane precaster, the second organosilane precaster being different from the first organosilane precaster, the second organosilane precaster being configured to eliminate defect sites and unreacted sites on a surface of the workpiece having the first layer and on the first layer; device.

13. 13. The device of claim 12, wherein the workpiece is silicon or aluminum oxide.

14. 13. The device of claim 12, wherein the first organosilane precast is dimethyldichlorosilane or dimethyldiethoxysilane.

15. 15. The device of claim 14, wherein the second organosilane precurser is N,N-dimethyltrimethylsilylamine.

16. 15. The device of claim 14, wherein the second organosilane preform is trimethylchlorosilane.

17. 13. The device of claim 12, wherein the first layer is a self-assembled monolayer.

18. 13. The device of claim 12, wherein the second organosilane precast has at least the same chain length as the first organosilane precast.

19. 13. The device of claim 12, wherein the defect sites are hydroxyl groups.

20. The device of claim 12 , wherein the workpiece is a portion of a MEMS device.

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