Patent Application
20130168377
Fabrication of a semiconductor wafer may involve the formation of a dielectric or insulating film or layer on semiconductor material, such as silicon. For example, a silicon dioxide layer may be formed on a silicon wafer via oxidation. This is generally accomplished by thermal oxidation wherein the wafer is exposed to an oxidizing environment at an elevated temperature.
Thermal oxide may be grown in a diffusion furnace or process tube, which may be oriented either vertical or horizontal, at temperatures from 800° C. to 1200° C. using either a “wet” or “dry” growth method. Wet oxides may be grown pyrogenically using hydrogen and oxygen gases that are ignited in a combustion or torch chamber to form high purity steam or water vapor that is injected or otherwise introduced into the diffusion furnace.
The use of steam or water vapor accelerates oxide growth which occurs at the silicon/oxygen interface and grows outwardly from the silicon. As the oxide grows thicker, the rate of growth decreases because it takes longer for the oxygen atoms to penetrate the oxide and reach the silicon interface where the oxygen atoms combine with the silicon atoms to form the oxide. Oxygen atoms diffuse through the formed oxide at high temperature to reach the silicon to form additional oxide. This reaction occurs faster with an increase in the temperature of the diffusion furnace or process tube.
A diffusion furnace system for processing semiconductor material typically utilizes a torch chamber formed of quartz and a process tube formed of either quartz or silicon carbide, depending on the temperature of the particular process being conducted with the system. For process temperatures greater than 900° C., such as employed for oxidation or diffusion processes, the process tube is typically formed of silicon carbide to withstand the relatively high process temperature.
One aspect of the invention is a system for processing semiconductor material. The system comprises a process chamber to process semiconductor material therein and a fluid source to introduce a process fluid into the process chamber for processing the semiconductor material. The process chamber includes a first joint segment formed of a first material having a first coefficient of thermal expansion and the fluid source includes a second joint segment formed of a second material having a second coefficient of expansion that is different from the first coefficient of expansion. The system further comprises an adapter, formed of the second material, joined to the first joint segment and the second joint segment to fluidly couple the fluid source to the process chamber.
Another aspect of the invention is a diffusion furnace system for oxidizing semiconductor material. The diffusion furnace system comprises a process tube to process semiconductor material therein and a torch chamber to generate water vapor for introduction into the process tube to create an oxidizing atmosphere for the semiconductor material. The process tube includes a ball joint segment that is formed of silicon carbide and has an orifice extending therethrough and the torch chamber includes a socket joint segment that is formed of quartz. The system further comprises an adapter, which is formed of quartz, fluidly coupling the torch chamber to the process tube. The adapter includes a first portion that extends into the orifice of the ball joint segment of the process tube and a second portion having a ball configuration engaged with the socket joint segment of the torch chamber to form a joint therebetween.
A further aspect of the invention is an adapter for fluidly coupling a torch chamber to a process tube of a diffusion furnace system for processing semiconductor material. The process tube includes a ball joint segment with an orifice and the torch chamber includes a socket joint segment that is configured to receive the ball joint segment of the process tube. The torch chamber is formed of quartz and the process tube is formed of silicon carbide. The adapter comprises an adapter body formed of quartz material and includes a throughbore extending along a length thereof. The adapter body includes a tubular portion that is adapted to be inserted into the orifice of the ball joint segment of the process tube and a ball joint segment located at an end of the tubular portion that is adapted to engage with the socket joint segment of the torch chamber to form a ball-and-socket joint therebetween.
Another aspect of the invention is a method of coupling a torch chamber to a process tube of a diffusion furnace system for processing semiconductor material. The process tube includes a male joint segment with an orifice extending therethrough and the torch chamber includes a female joint segment that is configured to receive the male joint segment, the torch chamber being formed of quartz and the process tube being formed of silicon carbide. The method comprises acts of providing an adapter body that is formed of quartz material and includes a throughbore extending along a length thereof. The adapter body includes a tubular portion and a male joint segment located at an end of the tubular portion, the male joint segment of the adapter having a configuration that mimics the male joint segment of the process tube. The method further comprises inserting the tubular portion into the orifice of the male joint segment of the process tube, and engaging the male joint segment of the adapter with the female joint segment of the torch chamber to form a joint therebetween.
Various embodiments of the invention will now be described, by way of example, with reference to the accompanying drawings, in which:
An adapter is provided for fluidly coupling a process chamber, such as a diffusion furnace or a process tube, and a fluid source, such as a torch chamber or combustion chamber, of a system for processing semiconductor material. The process chamber, which may be a diffusion furnace and the fluid source, which may be a torch chamber, may include joint segments or connectors that are configured to be joined or connected directly together to fluidly couple the torch chamber to the furnace for introducing a fluid, such as an oxidizing gas or vapor, into the process chamber of the furnace from the torch chamber to create a suitable atmosphere within the furnace for processing the semiconductor material.
The system may include a diffusion furnace and a torch chamber that are formed of materials having different coefficients of thermal expansion. Rather than engaging with or connecting the joint segment or connector of the torch chamber directly to the joint segment or connector of the diffusion furnace, the system may include an adapter that is configured to couple the joint segments of the torch chamber and the diffusion furnace together while accommodating the differences in thermal expansion between the materials. In this manner, the adapter may substantially reduce, if not eliminate, potential stress on the joint segments of the torch chamber and the diffusion furnace that may otherwise occur were the joint segments connected directly to each other and to experience different amounts of thermal expansion therebetween during use of the system.
The first connector or joint segment 26 may have a male configuration and the second connector or joint segment 28 may have a female configuration that receives the male joint segment, as shown in
For some applications, the process chamber 22 and the fluid source 24, including their respective connectors or joint segments 26, 28, may be formed of materials having different coefficients of thermal expansion. For example, the process chamber 22, including its joint segment 26, may be formed of a material having a coefficient of thermal expansion that is greater than the material used to form the fluid source 24 and its joint segment 28. Operating such a system at high temperatures, such as may be required for oxidation or diffusion processes for semiconductor material, can cause the ball joint segment 26 of the process chamber 22 to experience a greater amount of thermal expansion relative to the socket joint segment 28 of the fluid source 24. Such an arrangement may lead to potential damage to or failure of one or both of the joint segments due to the greater expansion of the ball joint segment within the socket joint segment.
In one embodiment, the system 20 is a diffusion horizontal furnace system for processing one or more semiconductor wafers 32, such as silicon wafers, at high temperature, for example, greater than 900° C. As known in the art, such a system may be utilized for thermal oxidation of silicon wafers 32 that results in the formation of a dielectric or insulating layer or film of silicon dioxide on each semiconductor wafer.
The fluid source may include a torch chamber 24 to generate water vapor for introduction into the process tube 22 to create an oxidizing atmosphere for the semiconductor material using a process as should be apparent to one of skill in the art. For example, hydrogen H2 and oxygen O2 gases may be introduced and ignited within the torch chamber 24 to produce high purity steam or water vapor H2O that then flows into the process tube 22, such as illustrated in
The torch chamber 24 may formed of quartz and the process tube 22 may be formed of silicon carbide, which thermally expands at a rate that is greater than quartz. This difference in thermal expansion can lead to damage or even failure of the quartz material of the torch chamber, caused by the greater expansion of the ball joint segment 26 within the socket joint segment 28, which could lead to the introduction of unwanted external air of other contaminants into the process tube. Robustness of such a furnace configuration highly depends on the skill of the personnel when setting-up and operating the system.
To substantially reduce, if not eliminate, potential damage to the joint of such a system, it may be desirable to couple the torch chamber 24 and the process tube 22 with an adapter or coupler that accommodates the differences in thermal expansion between joint segments, such as may occur with the use of different materials.
In one illustrative embodiment shown in
As illustrated in
In one illustrative embodiment shown in
The first portion 40 may be configured to be inserted into the orifice 30 of the ball joint segment 26 of the process tube 22 so that the ball joint segment extends along the exterior of the adapter. In this manner, thermal expansion of the ball joint segment 26 that is greater than thermal expansion of the adapter 34 will create minimal, if any, stress on the adapter. In one embodiment, the first portion 40 may have a tubular configuration that fits closely within the ball joint segment 26 of the process tube and passes process fluid into the orifice.
The second portion 42 of the adapter body 34 may be configured to engage with the socket joint segment 28 of the torch chamber 24 to form a joint therebetween. In one embodiment, the second portion 42 has a ball configuration that mimics the ball joint segment 26 of the process tube 22.
The adapter 34 may be configured limit insertion of the first portion into the orifice of the process tube. In one embodiment, the adapter may include a shoulder 44 between the first and second portions that is adapted to engage an end of the ball joint segment.
The adapter 34 may employ any size and/or configuration suitable for coupling a torch chamber to a process tube of a furnace system. In one embodiment, the adapter may have a length L1 of 55.4 mm with a throughbore 38 having a diameter D1 of 42 mm extending along the length of the adapter. The first portion 40 of the adapter may have a tubular configuration with a length L2 of 30 mm for insertion into the orifice of the ball joint segment of the process tube. The first portion 40 may have an outer diameter D2 of 46 mm for insertion into an orifice that has a diameter of 50 mm. The second portion 42 of the adapter may have a ball configuration for engaging with a socket joint segment of the torch chamber. The second portion 42 may have a diameter D3 of 50 mm at the end of the adapter that increases to a diameter D4 of 75 mm in a direction toward the first portion of the adapter. The second portion 42 may have a spherically shaped surface 46 with a radius R1 of 37.5 mm to form the ball joint configuration. It is to be appreciated that these dimensions are exemplary and other adapter configurations are contemplated as should be apparent to one of skill in the art.
The adapter may be fabricated from quartz material using any suitable manufacturing process as should be apparent to one of skill in the art. For example, and without limitation, the quartz adapter may be fabricated using electrical fusion or flame hydrolysis techniques. If desired, the adapter may be formed of other suitable materials using manufacturing techniques as should be apparent to one of skill in the art.
The invention has been described above in conjunction with a diffusion furnace system for oxidizing semiconductor material. However, it is to be understood that aspects of the invention may be employed with other systems for processing a semiconductor material, as should be apparent to one of skill in the art.
It should be understood that the foregoing description of various embodiments of the invention are intended merely to be illustrative thereof and that other embodiments, modifications, and equivalents of the invention are within the scope of the invention recited in the claims appended hereto. Although aspects of the invention have been described with reference to illustrative embodiments, aspects of the invention are not limited to the embodiments described. Additionally, aspects of the invention may be used alone, or in any suitable combination with other aspects of the invention.
