TW201413049A - Process gas flow guides for large area plasma enhanced chemical vapor deposition systems and methods - Google Patents

Abstract

The present invention provides methods and apparatus for a gas diffusion assembly in a deposition processing chamber. The invention includes a backing plate having an inlet for providing a process gas to a process chamber, a diffusion plate including a plurality of apertures for allowing the process gas to flow into the process chamber, a blocking plate disposed between the backing plate and the diffusion plate and including a plurality of apertures, and at least one gas flow guide disposed between the blocking plate and the backing plate and adapted to direct process gas flow laterally. Numerous additional features are disclosed.

Description

Process gas for systems and methods for large area plasma enhanced chemical vapor deposition Body flow guiding element

This invention relates to the manufacture of electronic devices, and more particularly to a process gas flow directing element for systems and methods for large area plasma enhanced chemical vapor deposition.

One of the main steps in the manufacturing process of modern electronic devices is to form a film on a substrate by chemical reaction of a gas. This deposition process is generally referred to as chemical-vapor deposition (CVD). A conventional thermal CVD process supplies a reactive gas to the surface of the substrate where a thermally induced chemical reaction is performed to form the desired film layer. Plasma-enhanced CVD (PECVD), on the other hand, increases the excitation and/or dissociation of reactive gases by applying radio-frequency (RF) energy. On the reaction zone near the surface of the substrate, resulting in Plasma. The highly reactive species in the plasma reduce the amount of energy required to generate a chemical reaction, and the temperature required for such a CVD process can be reduced compared to conventional thermal CVD processes.

Low temperature polysilicon process, for example, for manufacturing flat panel display The process of the curtain is performed in a process chamber, which typically includes a gas distribution assembly through which the gas system is introduced into the process chamber. The gas distribution assembly is typically used in a PECVD chamber to evenly distribute the gas introduced into the chamber onto the surface of the substrate after it is introduced into the chamber. In general, evenly distributing the gas over the surface of the substrate provides better uniform deposition characteristics on the surface of the substrate located in the process chamber.

In general, the gas distribution component contains a grounded gas An inlet manifold is connected to the gas source to provide gas to the process chamber. The gas inlet manifold allows gas to flow into the gas diffuser to evenly direct the gas into the PECVD chamber above the surface of the substrate. Referring to the conventional PECVD chamber 10 illustrated in FIG. 1 , the gas diffusion system 100 is in direct communication with the PECVD chamber 10 and typically includes a backing plate 102 having a gas inlet 104, a baffle plate 106, and a diffuser plate 108 for The gas is evenly dispersed from at least a region of the substrate from a single gas feed line and minimizes chaotic aerodynamic flow. The baffle 106 is typically an annular plate assembly having a plurality of very fine holes therethrough to evenly disperse gas from the inlet 104 into the space 110 above the diffuser plate 108. The gas is usually supplied via a single gas line in which the reactants and carrier gases have been mixed to provide a high concentration of gas. A partial area in the center of the baffle 106. The diffuser plate 108 is also generally a planar, annular assembly having a plurality of holes that are larger than the holes of the baffle plate 106, and the gas system is provided through the holes of the diffuser plate 108 or in a manner that diffuses through the holes of the diffuser plate 108. A uniform concentration of gas is on the substrate.

Despite the configuration as described above, the inventors of the present invention have discovered that In some cases, the deposition rate of the substrate regions produced by the gas diffusion system 100 of the prior art is not uniform. Therefore, methods and apparatus that have a more uniform deposition rate over the area of the substrate are desirable.

The present invention relates to a gas diffusion assembly for use in a deposition process chamber Method and device. The gas diffusion assembly comprises: a back plate having an inlet for supplying a process gas to a process chamber; a diffusion plate including a plurality of openings for allowing process gas to flow into the process chamber; and a barrier plate disposed on the back Between the plate and the diffuser plate, the baffle plate includes a plurality of openings; and at least one air flow guiding member disposed between the baffle plate and the back plate is adapted to guide the lateral flow of the process gas.

In some embodiments, the present invention provides a low temperature polysilicon (polysilicon) process chamber system. The system includes a process gas supply, a susceptor for supporting a substrate, and a gas diffusion assembly. The gas diffusion assembly includes: a back plate having an inlet coupled to the process gas supply; a diffusion plate including a plurality of openings for allowing process gas to flow to the substrate; and a barrier plate, The baffle plate is disposed between the back plate and the diffuser plate, and the baffle plate comprises a plurality of openings; and at least one airflow guiding element is disposed between the baffle plate and the back plate, and is adapted to laterally guide the flow of the process gas.

In other embodiments, the present invention provides a method of flowing process gas into a process chamber. The method includes: determining a region on a substrate that otherwise receives a relatively low deposition rate; and directing the process gas laterally to flow over a substrate between a backplane and a diffuser plate in other cases A region of relatively low deposition rate is received on the substrate.

In order to better understand the above and other aspects of the present invention, the preferred embodiments are described below, and in conjunction with the drawings, the detailed description is as follows:

10‧‧‧PECVD chamber

100, 200, 200'‧‧‧ gas diffusion modules

102, 202‧‧‧ Backplane

104, 204‧‧‧ entrance

106, 206‧‧‧Baffle

108, 308‧‧‧ diffusing plate

110‧‧‧ space

210‧‧‧Internal airflow guiding element

212, 212'‧‧‧ External airflow guiding element

700, 800‧‧‧ thickness map

702‧‧‧Low deposition rate region

704‧‧‧High deposition rate region

900‧‧‧ method

902~908‧‧‧ Process steps

A, B, C, C’, C’‧‧‧ size

M‧‧‧ circled parts

Figure 1 is a schematic diagram showing an example of a plasma enhanced chemical vapor deposition chamber of the prior art.

2A is a top exploded view of an example of a gas diffusion assembly (the diffuser is omitted for simplicity) in accordance with some embodiments of the present invention.

2B is a top plan view showing an example of a gas diffusion assembly (the diffusion plate is omitted for simplicity) in accordance with some embodiments of the present invention.

Figure 3 is a cross-sectional view showing an example of a gas diffusion assembly in accordance with some embodiments of the present invention.

4 is an enlarged cross-sectional view of the exemplary gas diffusion assembly encircling portion M of FIG. 3 in accordance with some embodiments of the present invention.

Figure 5A is a simplified rear cross-sectional view of a portion of one example of a gas diffusion assembly in accordance with some embodiments of the present invention.

Figure 5B is a simplified rear cross-sectional view of a portion of a gas diffusion assembly in accordance with another example of some embodiments of the present invention.

FIG. 6 is a schematic view showing an example of an internal airflow guiding member disposed around a gas inlet (the barrier plate and the diffusion plate are omitted for brevity) according to some embodiments of the present invention.

Figure 7 is a graph of the relative deposition rate produced in the region of the substrate using conventional gas diffusion assemblies of the prior art.

Figure 8 is a graph of the relative deposition rate produced by regions of the substrate using the gas diffusion assembly of the present invention.

Figure 9 is a flow chart showing an exemplary method of flowing a gas through a gas diffusion module in accordance with some embodiments of the present invention.

The present invention provides an improved method and apparatus for chemical vapor deposition A uniform deposition rate is achieved. In particular, the present invention facilitates more uniform deposition when manufacturing displays of low temperature polysilicon (LTPS) over large areas (eg, substrates greater than 730 mm x 920 mm). However, the invention is also applicable to other processes, sizes, and configurations.

Compared to the screen of amorphous germanium, LTPS liquid crystal display (Liquid Crystal Display (LCD) PECVD technology enables the manufacture of active array display screens to be faster and more integrated. Amorphous germanium Thin film transistors (TFTs) are deposited on large substrates, facilitating the active array industry rather than using single crystal germanium on the wafer. Despite the huge investment in existing amorphous germanium technology, polysilicon provides an additional approach for some applications. The larger and more uniform particles of polycrystalline germanium make the electron flow 100 times faster than the amorphous germanium (a-Si) with unequal size particles, thus achieving higher resolution and faster rate. In addition, the row/column driver electronics do not surround the screen area, but are integrated into the glass substrate, thereby reducing wiring between the TFT section and the pixels. Therefore, LTPD pixels can be more closely packed to a density of 200 dpi and above.

There are several important types of SiOx layers used in the LTPS process. This Three of these layers include a gate insulator (GI) layer, an interlayer dielectric (ILD) layer, and an amorphous precursor buffer layer. The uniformity of thickness of these SiOx layers, especially GI SiOx, is important for the success of LTPS manufacturing. The uniformity and characteristics of SiOx film thickness have been found to be significantly related to process gas flow distribution. Therefore, for uniform SiOx film deposition, it is important to produce a uniform process gas flow over a large area substrate.

Current systems for LTPS gas distribution rely on gas barriers or changes Stream (deflector) board. The barrier layer helps to regionally increase the SiOx uniformity in the center of the substrate region. However, today's barriers distribute the gas evenly across all lateral directions. The inventors of the present invention found that even the lateral distribution cannot address the unevenness caused by other factors affecting the film thickness. These factors include the electrode distance From factors such as the distance between the diffuser plate and the susceptor, plasma concentration, gas flow rate, and other similar factors, many of these factors are not easily adjusted because of the need for other layers or other The physical characteristics of the change. Thus, the inventors of the present invention have found that when the baffle provides an average lateral distribution of gas, high and low deposition rate patterns occur in a particular region. In particular, this pattern includes a high deposition rate along two intersecting diagonal lines extending from the corners to the corners of the substrate. Again, this pattern contains a region of low deposition rate that is near the center of the relatively long (eg, about 2500 mm) side of the substrate. This particular pattern is referred to as a "butterfly pattern" and the appearance of such a deposited pattern is a limiting factor that severely affects the SiOx thickness uniformity of the LTPS process.

The invention controls the process gas on the side between the back plate and the diffusion plate To flow, while overcoming the problem of butterfly patterns. The gas diffusion assembly of the present invention provides a gas flow directing element that affects the lateral flow of gas from the gas inlets on the diffuser plate, rather than the art of distributing the process gases laterally evenly. In particular, the internal gas flow directing element is used to direct more gas to the region of the substrate having a lower deposition rate, and the external gas flow directing element is used to reduce the rate of gas deposition to the substrate with a higher gas deposition rate. The vertical space of the area. In other words, by designing the side of the gas flow pattern between the backing plate and the diffusing plate, the reverse phase is matched to the other side due to the uniform lateral gas flow distribution between the backing plate and the diffusing plate. The deposition rate pattern, the present invention provides a gas diffusion assembly that improves the uniformity of the deposition rate over the substrate area.

In more detail, in order to reduce the center-crossing The higher deposition rate of the diagonal, and the lower deposition rate along the center of the long side, the four internal gas flow directing elements are disposed between the baffle and the backing plate to form an opening for lateral gas flow to the middle of the long side of the substrate . In some embodiments, five or more, three or fewer internal airflow guiding elements can also be used. The opening facing the upper region of the long side of the substrate is greater than (eg, more than twice) the opening facing the region above the short side of the substrate. Such internal airflow directing elements also form a barrier to prevent lateral gas flow to the corners of the substrate. In addition, an external airflow directing element for reducing the vertical space between the backing plate and the diffusing plate is configured to reduce the flow of gas to the central intersecting diagonal. In some embodiments, four external airflow directing elements are used that are arranged in a radial pattern. In other embodiments, five or more, three or fewer external airflow guiding elements can also be used. In some embodiments, the external airflow directing element can be shaped to match the shape of the relatively high deposition rate region when the guiding element is not disposed. In other words, the panel used to reduce the vertical space between the backing plate and the diffusing plate can be shaped to match or correspond to observable inhomogeneities in conventional chambers (eg, high spots or deposition peaks). )).

Please refer to FIG. 2A, which illustrates a gas according to an embodiment of the invention. An example of the diffusion assembly 200 is an exploded view. The diffuser plate is not shown, so other components can be displayed. The gas diffusion assembly 200 includes a rectangular backing plate 202 having an inlet 204 formed thereover. In some embodiments, the backing plate 202 functions as a removable upper or top plate of one of the process chambers. It may be noted that the gas diffusion assembly 200 of the embodiments of the present invention is suitable as a direct replacement for the gas diffusion assembly 100 of the conventional chamber 10. Therefore, the gas diffusion assembly 200 of the embodiment of the present invention is added The existing chamber 10 (instead of the conventional gas diffusion assembly 100) is a new chamber in accordance with an embodiment of the present invention. The inlet 204 is covered by a disc-shaped deflector or baffle 206 that includes a radially aligned opening for gas to flow from the inlet 204 to the chamber. In Figure 2A, only a small portion of the opening is shown in the baffle 206.

In some embodiments as shown in Figure 2A, internal airflow guidance Element 210 is disposed about inlet 204 and between backing plate 202 and baffle 206. The internal airflow directing element 210 is a solid, curved strip that can be placed at any desired location between the backing plate 202 and the baffle 206 to prevent lateral airflow in certain directions and allow other Lateral airflow in the direction. The height of the internal airflow directing element 210 determines the distance between the backing plate 202 and the baffle 206. This distance has been found to affect the deposition rate of the central region of the substrate, and therefore, the height of the internal gas flow directing element 210 is carefully selected to avoid localized deposition peaks or valleys from appearing in the center of the substrate.

In some specific embodiments shown, four internal airflows The conductive elements 210 (only three are visible due to the baffle 206) are disposed around the perimeter of the baffle 206, but at a distance from the edge of the baffle 206. Other separation distances can also be used. The internal airflow guiding element 210 is positioned to form two larger lateral openings facing the upper region of the center of the long side of the substrate after positioning, and two smaller ones of the upper region of the center of the short side of the substrate facing the positioning Opening. Thus, the positioning of the internal airflow directing element 210 is adapted to (1) prevent lateral gas from flowing out of the region above the corner of the substrate; (2) allow some lateral gas to flow into the short side of the substrate. The upper area of the center; (3) allows more lateral gas to flow to the upper area of the center of the long side of the substrate. Other architectures can also be used for different processes.

In some embodiments, the internal airflow directing element 210 can be aluminum or Made of other suitable materials. The internal airflow directing element 210 can be adapted to be securely secured to the backing plate 202. Similarly, the baffle 206 can be adapted to be securely secured to the internal airflow directing element 210. More details regarding the internal airflow directing element 210 are provided below and referenced to Figures 5A, 5B, and 6.

The gas diffusion assembly 200 of the embodiment of the present invention may further include external air Flow directing element 212. The external airflow directing element 212 can be implemented as a thin rectangular or elliptical spacer that radiates from the inlet 204 to the corner of the backing plate 202. Other shapes may also be used in some embodiments. The external airflow directing element 212 can be securely attached to the backing plate 202 for reducing the vertical area between the backing plate 202 and the diffusing plate. Any suitable shape can also be used depending on the process or other factors. In some embodiments, the shape of the external airflow directing element 212 can be selected to match the deposition rate (eg, thickness) pattern that would otherwise be formed on the substrate when the external airflow directing element 212 is not disposed. In some embodiments, the external airflow directing element 212 can be implemented as a planar aluminum plate and can include square, circular, or beveled edges.

In an alternate embodiment of the gas diffusion assembly 200', the external air flow The guiding elements 212 can have different shapes and/or different thicknesses to correspond to or be related to a deposition rate pattern formed in the process other than when the external airflow guiding element 212 is not provided. For example, as shown in Figure 2B, the external airflow guide element The piece 212' may have a teardrop or pear shape to more closely match the deposition pattern formed in other cases when the external airflow directing element is not provided.

3 and 4 illustrate gas diffusion in accordance with an embodiment of the present invention A cross-sectional view of an example of assembly 200. Fig. 4 is an enlarged view showing the portion M of the gas diffusion unit 200 of Fig. 3; In particular, such figures illustrate cross-sectional views of the internal airflow directing element 210 disposed between the backing plate 202 and the baffle 206 and disposed about the inlet 204. The diffuser plate 308 is shown below the baffle 206. Please note that the openings of the diffuser plate 308 and the baffle 206 are not shown. Again, please note that the external airflow directing element 212 is not shown in such cross-sectional views.

FIG. 5A illustrates a portion of one example of the gas diffusion assembly 200 Simplify the schematic diagram of the rear section. This particular schematic is provided to show a portion of the dimension that can be adjusted to achieve the desired lateral gas flow to provide a more uniform deposition rate for the regions of the substrate. In detail, the dimension A is the vertical height of the space between the back plate 202 and the diffusion plate 308, the dimension B is the vertical height of the space between the barrier plate 206 and the diffusion plate 308, and the dimension C is the external airflow guiding element 212 and diffusion. The vertical height of the space between the plates 308. Therefore, as shown in FIG. 5A, the height of the internal airflow guiding member 210 is adjusted to the size B, and the thickness of the external airflow guiding member 212 is adjusted to the dimension C.

Please refer to FIG. 5B, which illustrates another embodiment in accordance with the present invention. A simplified rear cross-sectional view of a portion of a gas diffusion assembly 200'. As noted above, this figure shows the size of the portion that can be sized to achieve the desired lateral airflow that provides a more uniform deposition rate over the area of the substrate. rate. Specifically, the dimension A is the vertical height of the space between the back plate 202 and the diffusion plate 308, the dimension B is the vertical height of the space between the barrier plate 206 and the diffusion plate 308, and the dimension C' is the external airflow guiding element 212' and The minimum vertical height of the space between the diffuser plates 308, the dimension C" is the maximum vertical height of the space between the outer airflow directing element 212' and the diffuser plate 308. Thus, as shown in Fig. 5B, the inner airflow directing element 210 The height B is adjusted in size, and the shape of the external airflow guiding member 212' is adjusted by the size C' and the size C".

Figure 6 shows the surrounding gas inlet 204 and fixed to the backing plate 202 An enlarged and reversed schematic view of one of the four internal airflow guiding elements 210. Barrier plates and diffusers are not shown. As described above, the internal airflow directing element 210 is positioned to form two larger lateral openings (labeled as dimension D) facing the upper region of the center of the long side of the substrate after positioning, and two smaller openings (labeled as Dimension E) The upper area of the center of the short side of the substrate facing the positioning. Thus, as described above, the positioning of the internal airflow directing element 210 is adapted to (1) prevent lateral gas flow from regions above the corners of the substrate; (2) allow certain lateral gas flows toward the upper region of the center of the short side of the substrate; (3) Allow more lateral gas flow toward the upper region of the center of the long side of the substrate.

Figures 7 and 8 illustrate thickness maps 700 and 800 of film deposition, The chambers commercially available from Applied Materials, Inc. of Santa Clara, Calif., may be used with or without the diffusion assembly of the present invention.

More specifically, the thickness map 700 of FIG. 7 shows the resulting area on a relatively large substrate using conventional gas diffusion assemblies of the prior art. Relative deposition rate. The resulting butterfly pattern includes a low deposition rate region 702 that is near the center of the relatively long (eg, about 2500 mm) side of the substrate, and a high deposition rate region 704 that extends across the corners of the substrate to the corners. Corner line. Such a degree of film thickness unevenness is problematic.

The thickness map 800 of Fig. 8 shows the relative deposition rate produced on the area of the substrate using the gas diffusion assembly of the embodiment of the present invention. In accordance with the present invention, internal and external airflow directing elements are used to distribute the gas laterally between the backing plate and the diffusing plate. The gas diffusion assembly of the embodiment of the present invention achieves a reduction in thickness variation as compared to the thickness variation caused by the gas diffusion assembly of the prior art in Fig. 7, which indicates that the uniformity can be improved.

FIG. 9 is a flow chart showing an exemplary method 900 of flowing a gas through a gas diffusion assembly in accordance with some embodiments of the present invention. During execution, a region of a relatively low deposition rate on the test substrate is determined (902). In some embodiments, regions of relatively high deposition rates on the test substrate can also be determined (904). Based on the determination of the high and low deposition rates, the internal gas flow directing element is disposed around the gas inlet and between the backing plate and the baffle to direct the process gas laterally toward the substrate region having a relatively low deposition rate on the test substrate. Upper area (906). In some embodiments, the internal gas flow directing element can be additionally configured to prevent process gases from flowing laterally to areas on the test substrate that have a relatively high deposition rate on the substrate area. Additionally, the external airflow directing element can be disposed on the substrate area on the test substrate having a relatively high deposition rate (908).

In summary, although the invention has been disclosed above in the preferred embodiments, It is not intended to limit the invention. A person skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, the scope of the invention is defined by the scope of the appended claims.

200‧‧‧ gas diffusion components

202‧‧‧ Backplane

204‧‧‧ Entrance

206‧‧‧Baffle

210‧‧‧Internal airflow guiding element

212‧‧‧External airflow guiding element

Claims (15)

A gas diffusion assembly comprising: a backing plate having an inlet for supplying a process gas to a process chamber; and a diffusion plate comprising a plurality of openings for allowing the process gas to flow into the process chamber; a barrier plate disposed between the back plate and the diffusion plate, the barrier plate comprising a plurality of openings; and at least one air flow guiding member disposed between the barrier plate and the back plate, suitable for guiding the The process gas flows laterally. The gas diffusion assembly of claim 1, wherein the at least one gas flow guiding element is adapted to direct the process gas to flow laterally toward a substrate and otherwise receive a lower deposition rate. One area. The gas diffusion module of claim 1, wherein the at least one gas flow guiding element is adapted to direct the process gas to flow laterally away from a region above a substrate that would otherwise receive a higher deposition rate. . The gas diffusion assembly of claim 1, wherein the at least one gas flow directing element comprises four internal gas flow directing elements disposed about the inlet. The gas diffusion module of claim 4, wherein the internal gas flow directing elements are adapted to direct the SiOx process gas laterally toward a region above a long side of a substrate. The gas diffusion module of claim 4, wherein the internal gas flow directing elements are adapted to direct the SiOx process gas laterally away from a region above a corner of a substrate. The gas diffusion assembly of claim 1, wherein the at least one internal gas flow guiding element is adapted to restrict lateral process gas flow from above a substrate to otherwise receive A region of higher deposition rate. The gas diffusion assembly of claim 1, wherein the at least one airflow guiding element comprises four external airflow guiding elements, the four external airflow guiding elements being disposed around the inlet. The gas diffusion module of claim 8, wherein the four external air flow guiding elements are adapted to limit the flow of the side of the process gas from above a center-crossing diagonal of a substrate One area. A low-temperature polysilicon process chamber system includes: a process gas supply; and a susceptor for supporting a substrate; a gas diffusion assembly comprising: a back plate having an inlet and coupling a process gas supply; a diffusion plate comprising a plurality of openings for allowing the process gas to flow to the substrate; a barrier plate disposed between the back plate and the diffusion plate, the barrier plate comprising a plurality of openings ;and At least one airflow guiding element disposed between the baffle and the backing plate is adapted to laterally guide the flow of the process gas. The low temperature polysilicon processing chamber system of claim 10, wherein the at least one gas flow guiding element is adapted to direct the process gas to flow laterally toward an area above the substrate, in other cases in the region. Lower will receive a lower deposition rate. The low temperature polysilicon processing chamber system of claim 10, wherein the at least one gas flow guiding element is adapted to direct the process gas to flow laterally away from a region above the substrate, the region being In case a higher deposition rate will be received. The cryogenic polysilicon processing chamber system of claim 10, wherein the at least one gas flow directing element comprises four internal gas flow directing elements disposed about the inlet. The low temperature polysilicon processing chamber system of claim 13, wherein the internal gas flow guiding elements are adapted to direct the SiOx process gas laterally toward a region above one of the long sides of the substrate, and laterally An area away from a corner of one of the substrates. A method of flowing a process gas into a process chamber, the method comprising: determining a region on a substrate that otherwise receives a relatively low deposition rate; directing the process gas laterally on a back plate and a diffusion plate Flowing between the substrate and otherwise receiving a relatively low deposition rate on the substrate An area; a region on a substrate that otherwise receives a relatively high deposition rate; and a process gas that laterally flows between a backing plate and a diffuser plate away from the substrate in other cases A region of relatively high deposition rate is received on the substrate.