JP3998700B2 - Lamp annealing equipment - Google Patents

Description

  The present invention relates to a lamp annealing apparatus used for oxidation, nitridation, heat treatment, and the like of a semiconductor wafer in a semiconductor device manufacturing process.

  In recent years, a lamp annealing apparatus capable of rapid heating and rapid cooling when an oxide film or a nitride film is formed on a semiconductor wafer has been used. A conventional lamp annealing apparatus is an apparatus that heats a semiconductor wafer placed in a quartz or metal chamber by light irradiation such as a xenon lamp, and the chamber has a plurality of processes required depending on processing steps. A gas source is connected.

  The structure of such a conventional lamp annealing apparatus will be described with reference to the drawings. FIG. 2 is a schematic view of a conventional lamp annealing apparatus. The conventional apparatus has a quartz or metal chamber 10 as shown in FIG. 2, and a lamp unit 1 composed of a xenon lamp or the like serving as a lamp light source in the chamber 10 and a quartz plate 11 that partitions the lamp unit 1. And a support ring 3 for horizontally supporting one semiconductor wafer 2 and a rotating cylinder 4 for placing the support ring 3 thereon.

  The rotating cylinder 4 can be rotated by a driving mechanism (not shown) to rotate the semiconductor wafer 2 in the chamber 10. Further, the chamber 10 is provided with a reflector (Al reflector) 7 for ensuring temperature stability on the inner bottom surface, and further, a gas supply line 5 for supplying a process gas into the chamber 1 and a processing gas. Is provided with a gas exhaust line 6.

  Further, in order to prevent the reflector 7 from being fogged during the heat treatment, a back gas supply line 8 for blowing back gas from the lower part of the chamber 10 toward the back surface of the semiconductor wafer 2 is provided, and this back gas supply line is provided. Reference numeral 8 is connected to a plurality of backside gas supply ports 12 branched into a plurality of holes and opened in the reflector 7, and backside gas is blown into the chamber 10 through the backside gas supply ports 12.

  A plurality of backside gas exhaust ports 13 for discharging the backside gas are opened in the periphery of the surface of the reflector 7, and each backside gas exhaust port 13 is connected to the backside gas exhaust line 9 and is connected to the backside gas from the chamber 10. Is supposed to be discharged. Further, a sensor (not shown) for temperature control is embedded in the backside gas supply line just below the reflector 7 so that the semiconductor wafer 2 has a uniform temperature distribution as a whole.

  When the semiconductor wafer 2 is heated using the conventional lamp annealing apparatus having such a structure, first, the semiconductor wafer 2 is carried into the chamber 10 from the carry-in port (not shown) and placed on the support ring 3. Place. Next, a desired process gas is supplied from the gas supply line 5 and a backside gas is supplied at the same time. The lamp unit 1 is turned on to heat and heat the semiconductor wafer 2 while rotating it.

  In this conventional lamp annealing apparatus, fogging may occur on the upper surface of the reflector 7 provided to ensure temperature stability due to outward diffusion (out diffusion) from the semiconductor wafer 2 during heat treatment. Therefore, in order to prevent the occurrence of fogging, nitrogen gas is blown out as a backside gas from the backside gas supply port 12 opened in the reflector 7 toward the backside of the semiconductor wafer 2 to blow out the out diffusion.

  However, the natural oxide film is thinly formed on the semiconductor wafer 2 before the heat treatment, and the natural oxide film reacts with the nitrogen gas as the backside gas to generate silicon oxide fine particles. Therefore, although the problem of out-diffusion can be solved by blowing nitrogen gas from the back side, a problem has arisen that the reflector is fogged by silicon oxide.

  Therefore, in order to solve this new problem, it has been confirmed that oxygen gas should be added to the nitrogen gas as the backside gas. However, the backside gas sometimes circulates to the wafer surface side through the gap of the support ring. As a result, depending on the amount of oxygen gas to be added, the element formation surface on the wafer surface side is oxidized and the transistor characteristics fluctuate. Is causing. Furthermore, there is a problem in that the gas on the back side and the process gas on the front side are poorly separable, and both gases wrap around.

  Thus, in the conventional lamp annealing apparatus, as shown in JP-A-2-280319, the flow rate of the process gas is controlled but the flow rate of the backside gas is not controlled. If the oxygen gas is not adjusted properly, the transistor characteristics will fluctuate, leading to defective products.

  The present invention provides a lamp annealing apparatus that prevents fogging of a reflector, stabilizes the heat treatment temperature, and prevents oxidation of an element formation surface on the semiconductor wafer surface side.

  The lamp annealing apparatus of the present invention has a lamp unit for heating in the upper part of the chamber and a reflector for stabilizing the temperature in the lower part of the chamber, and is mounted on a rotating cylinder in the chamber to rotate. In a lamp annealing apparatus having a structure in which a process gas is caused to flow on the element forming surface on the front side of the semiconductor wafer and a gas for preventing fogging of the reflector is caused to flow on the silicon surface on the back side, the gas flowing on the back side of the semiconductor wafer The separability of the process gas on the front side of the semiconductor wafer and the antifogging gas on the back side is improved by evacuating around the lower part of the outer periphery of the semiconductor wafer.

  The first effect of the lamp annealing apparatus of the present invention is that a device for diluting a desired gas is provided, so that nitrogen gas containing oxygen in the order of ppm can be stably supplied to the back surface of the semiconductor wafer, and silicon Generation of silicon oxide fine particles due to the reaction between the natural oxide film formed on the surface and nitrogen gas can be suppressed, fogging of the reflector can be prevented, and temperature stabilization can be achieved.

  The second effect is that the front surface and the back surface of the semiconductor wafer can be brought into contact with gases having different compositions, so that nitrogen gas containing oxygen in the order of ppm is supplied to the silicon surface on the back surface. Since nitrogen gas can be supplied to the element formation surface, oxidation of the element formation surface on the surface can be prevented while exhibiting the first effect.

  Next, an embodiment of the lamp annealing apparatus of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view of a lamp annealing apparatus of the present invention. The lamp annealing apparatus of the present invention has a quartz or metal chamber 10 as shown in FIG. 1, and the lamp unit 1 is divided into a lamp unit 1 composed of a xenon lamp or the like serving as a lamp light source. A quartz plate 11, a support ring 3 that horizontally supports the semiconductor wafer 2, and a rotating cylinder 4 on which the support ring 3 is placed are provided.

  The rotating cylinder 4 can be rotated by a driving mechanism (not shown) to rotate the semiconductor wafer 2 in the chamber 10. Further, the chamber 10 is provided with a reflector (Al reflector) 7a for ensuring temperature stability on the inner bottom surface, and further, a gas supply line 5 for supplying a process gas into the chamber 10 and a post-treatment A gas exhaust line 6 is provided for discharging the gas.

  Further, in order to prevent the reflector 7a from being fogged due to out-diffusion (out diffusion) from the semiconductor wafer 2 during the heat treatment, a back-side gas supply for blowing back gas from the lower part of the chamber 10 toward the back of the semiconductor wafer 2 is provided. A line 8 is provided, and the backside gas supply line 8 is branched into a plurality of lines and connected to a plurality of backside gas supply ports 12 opened in the reflector 7a, and the backside gas is supplied to the chamber through the backside gas supply port 12. 10 is blown out.

  A plurality of backside gas exhaust ports 13 for discharging the backside gas are opened at positions along the outer periphery of the reflector 7a on the bottom surface in the chamber 10 where the reflector 7a is installed. The port 13 is connected to the backside gas exhaust line 9 and discharges the backside gas from the chamber 10.

  That is, the backside gas supplied into the chamber 10 flows around the outer periphery of the reflector 7 a, flows into the backside gas exhaust port 13 through the gap with the rotating cylinder 4, and is discharged to the outside through the backside gas exhaust line 9. become. Further, a sensor (not shown) for temperature control is embedded in the backside gas supply line just below the reflector 7a so that the semiconductor wafer 2 has a uniform temperature distribution as a whole.

  The backside gas supplied to the backside gas supply line 8 is adjusted by providing mass flow controllers 15a, 15b, 15c, and 15d in the respective gas pipes so that the nitrogen gas and oxygen gas have a desired mixing ratio. The backside gas adjusted by the mass flow controllers 15 a to 15 d is supplied to the backside gas supply line 8 through the gas mixer 14. Further, in the present embodiment, the oxygen gas pipes are branched into three so that the supply amount of oxygen gas can be adjusted in stages, and mass flow controllers 15b, 15c, 15d are provided in the respective pipes so that they can be switched and used. I have to.

  The operation of the present embodiment will be described below with reference to FIG. In the case of heating the semiconductor wafer 2 using the lamp annealing apparatus of the present invention as shown in FIG. 1, first, the semiconductor wafer 2 is carried into the chamber 10 from the carry-in port (not shown) and rotated. Place on the support ring 3 resting on the cylinder 4.

  Next, a desired process gas is supplied from the gas supply line 5 and at the same time a back gas is supplied from the back gas supply line 8, the lamp unit 1 of the heating source is turned on, and the rotating cylinder 4 is rotated by a drive mechanism (not shown). Then, heating and heating are performed while rotating the semiconductor wafer 2.

  The process gas includes, for example, nitrogen gas, oxygen gas, ammonia gas, argon gas, water vapor, etc., and each process gas is adjusted by a mass flow controller (not shown), and the gas is changed according to oxidation, nitridation, heat treatment, etc. The type is selected, supplied from the gas supply line 5 into the chamber 10, and brought into contact with the surface side of the semiconductor wafer 2 for heat treatment.

  The temperature inside the chamber 10 can be kept constant by the reflector 7a. However, in order to prevent fogging of the reflector 7a caused by outward diffusion (out-diffusion) from the semiconductor wafer 2 during the heat treatment, Backside gas is supplied from the gas supply line 8. The supplied backside gas is exhausted from the backside gas exhaust line 9.

  At that time, the exhausted backside gas flows into the backside gas exhaust port 13 of the chamber 10 through the gap between the outer periphery of the reflector 7 a and the rotating cylinder 4, and is exhausted from the backside gas exhaust line 9 through the backside gas exhaust port 13. Since it has a structure, it is possible to improve the separation between the gas on the front surface side and the gas on the back surface side.

  That is, since the backside gas exhaust port 13 is conventionally provided directly in the periphery of the reflector, fogging often occurs in the periphery of the reflector. However, in the present invention, the backside gas is exhausted from the periphery of the reflector to exhaust the backside gas. Since it is made to flow and exhaust to the opening | mouth 13, the gas flow of the reflector whole surface is stabilized, and it becomes difficult to generate | occur | produce fogging.

  Moreover, the backside gas supplied to the backside gas supply line 8 is diluted and adjusted to have a desired mixing ratio by a plurality of mass flow controllers 15a to 15d, and is mixed by the gas mixer 14, ppm. Nitrogen gas containing oxygen of the order can be stably supplied to the back surface of the semiconductor wafer 2.

  For example, in the embodiment shown in FIG. 1, nitrogen gas is supplied as a backside gas by adjusting it to 10 l / min by the mass flow controller 15a, and oxygen gas is supplied to any of the mass flow controllers 15b, 15c, and 15d as necessary. The gas is mixed and supplied with nitrogen gas by the gas mixer 14. At this time, the mass flow controller 15b is adjusted to 100 cc / min, 15c is adjusted to 10 cc / min, and 15d is adjusted to 1 cc / min.

  As a result, it becomes possible to suppress the outward diffusion (out diffusion) from the semiconductor wafer 2 and the generation of silicon oxide fine particles due to the reaction between the natural oxide film formed on the silicon surface and nitrogen gas, and the fogging of the reflector 7a is prevented. To prevent temperature stabilization.

It is the schematic of the lamp annealing apparatus of this invention. It is the schematic of the conventional lamp annealing apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Lamp unit 2 Semiconductor wafer 3 Support ring 4 Rotating cylinder 5 Gas supply line 6 Gas exhaust line 7, 7a Reflector 8 Back surface gas supply line 9 Back surface gas exhaust line 10 Chamber 11 Quartz plate 12 Back surface gas supply port 13 Back surface gas exhaust port 14 Gas mixer 15a, 15b, 15c, 15d Mass flow controller

Claims (3)

A heating lamp unit in the upper part of the chamber, and a reflector for stabilizing the temperature in the lower part of the chamber. The element on the surface side of the semiconductor wafer mounted on the rotating cylinder in the chamber and rotating. In a lamp annealing device with a structure in which a process gas is flowed to the formation surface and a gas for preventing fogging of the reflector is flown to the silicon surface on the back side,
The gas flowing to the back side of the semiconductor wafer is exhausted around the lower part of the outer periphery of the reflector, thereby improving the separation between the process gas on the front side of the semiconductor wafer and the antifogging gas on the back side. A lamp annealing apparatus characterized by that.   2. The lamp annealing apparatus according to claim 1, wherein the process gas on the front side and the gas flowing on the back side are different gases.   3. The lamp annealing apparatus according to claim 1, wherein the gas flowing to the back side is a gas containing nitrogen and oxygen. 4.

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