Metallic material deposition method for integrated circuit manufacturing

Abstract: The improved material deposition process of the present invention utilizes a first, low temperature deposition step followed by a second, high temperature/high power deposition step. In the first deposition step a collimation plate (32) is placed between the sputtering target (18) and the substrate (12), such that a collimated stream of sputtered material is deposited upon the substrate (12). The collimated stream provides a seed layer (40) which aids in eliminating voids by partially filling the holes and grooves in the surface of the substrate (12). The second deposition step is conducted as a high temperature sputtering deposition. At the high temperature the sputtered material joins and flows with the seed layer (40), whereby the holes and grooves are more easily filled without voids and an improved planarized layer is achieved.

Description: The present invention relates generally to methods for depositing materials upon a semiconductor substrate, and more particularly to a two step deposition process wherein the first step includes a collimated relatively low temperature sputtering process and the second step utilizes a standard high temperature sputtering process. A standard process step in the manufacturing of integrated circuits involves the deposition of a metallic layer upon the surface of a wafer. Typically, the wafer surface has been previously etched in a plurality of locations, whereby the surface contains holes and grooves and is therefore not planar. It is the goal of the deposition step to uniformly and completely fill the holes and grooves and to achieve a generally planar outer surface after deposition has occurred. However, it is difficult to completely fill the holes and grooves, such that no voids exist. As is well known, the existence of voids can result in poor performance and defective devices. In an attempt to solve this problem, the prior art utilizes a deposition substrate temperature of approximately the melting point of the deposition material (approximately 450 degrees C. for aluminum) such that the deposited layer will tend to flow and completely fill the holes and grooves. The success of this process relies to a great extent upon the achievement of a uniform temperature throughout the substrate, such that the deposition and flow of the deposited material is substantially uniform and controlled. However, achieving a uniform temperature throughout the substrate requires rigorous temperature controls and can be difficult and time consuming. In US-A-4 970 176 a multiple step metallization process is disclosed with a first step in which a thick portion of a metal layer is disposed at a cold temperature ; the remaining amount of metal is deposited in a second step as the temperature is ramped up to allow the reflow of the metal layer. In EP-A-440 377 a process is disclosed according to the preamble of claim 1. The present invention is defined by a method according to claim 1. The improved material deposition method according to an embodiment of the present invention utilizes a first, low temperature deposition step followed by a second, high temperature deposition step. In the first deposition step a collimated stream of sputtered material is deposited upon the substrate. The collimated material provides a first layer which aids in filling the holes and grooves in the surface of the substrate. The second deposition step is conducted as a high temperature sputtering deposition. At the high temperature the sputtered material joins and flows with the first layer, whereby the holes and grooves are more easily filled, such that voids are eliminated and an improved planarized layer is achieved. It is an advantage of the present invention that it provides an improved material deposition process that does not require rigorous temperature controls. It is another advantage of the present invention that it provides an improved material deposition process that includes a first collimated low temperature deposition step and a second higher temperature step. It is a further advantage of the present invention that it provides an improved material deposition process wherein a collimation plate is utilized in a first deposition step, such that the holes and grooves in the surface of the substrate are coated with a substantial first layer, whereby the occurrence of voids is reduced and a more uniform second layer may be deposited thereon. These and other objects, features and advantages of the present invention will no doubt become apparent to those of ordinary skilled in the art after having read the following detailed description of the preferred embodiments which are illustrated in the several figures of the drawing. Fig. 1 is a side elevational view depicting the first step of the deposition process of the present invention; Fig. 2 is a side cross-sectional view depicting the substrate of the first deposition step of the present invention; and Fig. 3 is a side cross-sectional view depicting the second deposition step of the present invention and the resulting substrate. The present invention involves a two step deposition process which results in improved void filling and outer surface planarization in the deposition of materials upon a semiconductor substrate. Figs. 1 and 2 are depictions related to the first deposition step. As depicted in Figs. 1 and 2, a substrate 12 is held in position upon a suitable support 14. A target 18 is held upon a second support 20 and a plasma 24 is struck proximate the surface of the target 18, such that target material 28 is sputtered from the surface of the target 18 by the plasma 24. As depicted in Fig. 1, the sputtered material 28 projects away from the target surface 18 in random directions. A collimation plate 32 is disposed between the target 18 and the substrate 12, and held in place by a suitable support structure (not shown). The collimation plate 32 is disposed away from the plasma 24, such that the edges of the plate 32 are not exposed to the plasma. The collimation plate 32 includes a plurality of holes divided by thin, parallel walls, such that only sputtered material that is travelling from the target in a direction that is generally parallel to the walls will pass through the plate, such as material 36. While a broad range of dimensions of collimation plates may be utilized in the present invention, suitable results may be obtained with a honeycomb plate wherein the walls have a height of approximately 19.0 mm (0.75 inches) and the holes have a width at at their widest point of approximately 12.7 mm (one-half inch) whereby the collimation plate has an aspect ratio (length/width) of approximately 1.5. The collimation plate 32 may be composed of any material that is suitable for the environmental conditions within the deposition chamber, including aluminum and stainless steel. Fig. 2 is a close-up cross-sectional depiction of the substrate 12 following the first deposition step. As is depicted in Fig. 2, it is the purpose of the first deposition step to provide a seed layer 40 that is deposited upon the surface of the substrate 12. As is well known to those knowledgeable in the art related to the fabrication of integrated circuits, the surface of the substrate 12 will typically contain a plurality of holes and grooves, such as groove 50 shown in cross-sectional view in Fig. 2. The seed layer 40, owing to its collimated nature will form a thicker layer 52 on the bottom surface 51 of the groove 50 and a thinner layer 54 along the sides of the groove 50. The layer 56 outside of the groove will tend to have a thickness that is greater than the thickness 52 within the bottom of the groove 50. It is therefore to be understood that the collimated deposition layer 52 serves to substantially cover the bottom surface 51 of the groove 50 and to assure complete contact of the deposited material 52 with the bottom surface 51 of the groove 50. It is not necessary nor desired that the first layer 40 be heated to a temperature sufficient for it to flow, whereby the first deposition step may be conducted at a low temperature, such as from room temperature to approximately 100 degrees centigrade. Higher temperatures, short of the deposition material flow temperature could also be utilized, although it is not necessary to utilize such temperatures in the first step. The second step of the deposition process is generally depicted in Fig. 3. This second deposition step is preferably, although not necessarily, conducted in a different chamber from the first deposition step, and is conducted in a similar manner to the prior art deposition processes. It is to be understood that Fig. 3 depicts the substrate 12 in a close-up, cross-sectional view similar to Fig. 2, whereas the target and plasma of Fig. 3 are depicted in a side elevational view similar to Fig. 1. As depicted in Fig. 3, a target 70 composed of a suitable deposition material is sputtered by a plasma 74, such that deposition material 78 projects in random directions therefrom. The deposition material 78 is deposited in a layer 80 on top of the layer 40 that was created in the first deposition step. As is generally practiced in the art, the temperature of the second deposition step is approximately the flow temperature of the second deposition material, such that the second deposition layer tends to flow into the irregularities, such as the groove 84 in the layer 40 which mirrors the groove 50 in the substrate. The flow of the second deposition material layer 80 therefore fills the groove 84 and results in an improved overall deposition of combined layers 40 and 80 within the groove 50 of the substrate 12. It is therefore to be understood that the first deposition step, utilizing a collimated first layer assures that the bottom surface 51 of the groove 50 will be thoroughly coated with the deposition material. This feature is significant where the bottom surface 51 is a contact for an electrical connection. Owing to the temperature and power utilized in the second deposition step, the second deposition layer may both flow and grow into the first deposition layer, whereby the presence of voids in the grooves is substantially reduced and an improved overall deposited layer results. In the preferred embodiment deposition procedure the deposition material for both the first deposition step and the second deposition step is aluminum. The first deposition step was conducted in a first chamber at a temperature of approximately 50°C, a pressure of 2 mTorr, a power of 9 kw for 140 seconds which produced a first layer thickness within the holes and grooves of approximately 1200 angstroms (10 angstroms are equal to 1 nm) at the bottom 51 of the grooves. The second deposition step was conducted in a second chamber as a three part process wherein the first part was conducted at a starting temperature of approximately 50°C increasing to approximately 150°C, at a pressure of 4.0 mTorr, a power of 2 kw for 30 seconds, followed by a second part wherein the substrate heater was turned on to rapidly ramp up the wafer temperature to approximately 450°C, at a pressure of 4.0 mTorr, a power of 2 kw for 30 seconds, such that the deposition thickness of the second layer following the first two parts was approximately 2,600 angstroms. Thereafter, with the temperature and pressure remaining the same, the power was raised to 9 kw for 25 seconds, whereupon an additional layer of 5,000 angstroms was deposited. The temperature and power utilized in the third part of the second deposition step are sufficient to cause the material deposited in the second layer to flow into the holes and grooves to fill them and result in a generally planer outer sur-face. Additionally, the aluminum in the first layer tended to grow and bond with the aluminum deposited in the second layer. While the invention has been particularly shown and described with reference to certain preferred embodiments, it will be understood by those skilled in the art that various alterations and modifications in form and detail may be made therein.

Claims: A combined layer deposition process by sputtering with a first step of: a) sputter depositing a first layer (40) of a first material upon the substrate (12) at a temperature of the substrate between room temperature and 100°C and at a first deposition rate, wherein said sputtered first material is passed through a collimation plate (32) prior to the deposition thereof upon said substrate (12) thereby providing a seed layer covering the bottom of grooves in the substrate, wherein said first material is aluminum; characterized by a second step of b) depositing a second layer (80) of a second material without the use of a collimation plate upon said first layer (40) at a second deposition rate higher than the first deposition rate wherein said second material is aluminum; wherein the thickness of said first layer (40) is a fraction of the thickness of said second layer (80), wherein step b) comprises: depositing a first portion of the non-collimated second layer (80) of aluminum over the collimated first layer (40) during an increase of the substrate temperature to a first temperature; depositing a second portion of the non-collimated second layer (80) of aluminum over the collimated first layer (40) during a rapidly ramp up temperature; increase from said first temperature to a second temperature; this being approximately the flowing temperature of said second material ; and depositing a third portion of the non-collimated second layer (80) of aluminum on the first portion of the second layer (80) at said second temperature. The process of claim 1, wherein said temperature of the substrate during depositing said first layer (40) is approximately 50°C. The process of claim 1 or 2, wherein the second temperature is sufficient to cause the second material to flow to fill openings. The process of claim 3, wherein the second temperature is approximately 450°C. The process of any of claims 1 to 4, wherein said increase of the substrate temperature of depositing a first portion of the non-collimated second layer (80) is from approximately 50°C to approximately 150°C. The process of claim 5, wherein the time of depositing said first portion of said non-collimated second layer (80) is 30 seconds, the time of depositing the second portion of said non-collimated second layer (80) during said rapidly ramp up temperature increase is 30 seconds and the time of depositing the third portion (80) of said non-collimated second layer is 25 seconds. The process of any of the claims 1 to 6, wherein said collimation plate (32) has an aspect ratio of approximately 1,5. The process of any of the claims 1 to 7, wherein said first layer (40) and said second layer (80) are both deposited in the same processing chamber. The process of any of the claims 1 to 8, wherein said first layer (40) is deposited in a first processing chamber and said second layer (80) is deposited in a second processing chamber.

Inventors: KIEU HOA THI, TALIEH HOMOYOUN, TEPMAN AVI, WANG CHIEN-RHONE JEAN WANG, KIEU, HOA THI, TALIEH, HOMOYOUN, TEPMAN, AVI, WANG, CHIEN-RHONE (JEAN WANG)
Applicants: APPLIED MATERIALS INC, APPLIED MATERIALS, INC.
Application year: 1992
Main classification: H01L21
IPC codes: H01L21, C23C14, C23C28