Semiconductor device manufacturing: process – With measuring or testing – Optical characteristic sensed
Reexamination Certificate
2003-10-29
2004-11-09
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
With measuring or testing
Optical characteristic sensed
C702S155000
Reexamination Certificate
active
06815236
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of measuring a concentration of a material and a method of measuring a concentration of a dopant of a semiconductor device using the same. More particularly, the present invention relates to a method of measuring a concentration of a material contained in a boro-phosphorous silicate glass (BPSG) layer and a method of measuring a concentration of a dopant of a semiconductor device using the same.
2. Description of the Related Art
Recently, a degree of integration in semiconductor devices has increased to provide for faster processing of increased amounts of information and various techniques have been developed to facilitate information processing for a rapidly growing information society. In order to form increased numbers of patterns on a semiconductor substrate, a distance between patterns decreases and a width of a pattern narrows to form patterns having a relatively large step portion.
Generally, integrated patterns formed during manufacturing of a semiconductor device are transistors and various metal wirings formed on the semiconductor substrate. These integrated patterns are conductive, thus an insulation layer to insulate neighboring conductive layers should be formed between each pattern.
When the insulation layer is formed on the conductive pattern, which is formed on the semiconductor substrate, an upper surface of the insulation layer becomes uneven and crooked due to large stepped portions of the underlying patterns. Accordingly, when the conductive patterns and the insulation layers are repeatedly formed on the underlying patterns and layers, the unevenness of the layers formed later becomes significant, ultimately resulting in a formation of a device that does not function as a semiconductor device. Therefore, a method of forming an insulation layer filling gaps between patterns having large stepped portions and narrow intervals without forming internal voids and accomplishing planarization is an important technique.
An insulation layer is formed by depositing boro-phosphorous silicate glass (BPSG) because the gap-filling property or the planarizing property is improved by heating the deposited layer. A thus-formed BPSG layer has a good reflowing characteristic accompanying a property of changing viscosity rapidly through heating at a temperature of about 850° C. The planarizing degree of the BPSG layer is different depending upon the concentration of dopants contained in the BPSG layer at an identical temperature. Therefore, BPSG insulation layers having different dopant concentrations exhibit different insulating properties.
In order to lower a processing temperature during semiconductor processing, a concentration of dopants, such as boron (B), phosphorus (P) and the like, in silicon oxide (SiO
2
), which is a primary component of the BPSG layer, is controlled to accomplish a good planarizing property at a low temperature. Accordingly, the measure of the intensity of the dopants, including boron and phosphorus, in the BPSG insulation layer is a very important inspection step.
A Fourier Transform Infrared Ray measurement (FT-IR measurement) may be used to analyze components contained in a layer.
A measuring instrument of an FT-IR analyzer is used for performing the FT-IR measurement. An absorption intensity distribution of IR for a target material is illustrated as a spectrum. When a radiant light passes through a layer of solid, liquid or gas, electrons, composing an atom, a molecule or an ion, absorb the radiant light to be transferred to an energy level corresponding to an absorbed photon energy of the radiant light. The difference between the electron energy levels is inherent to each chemical species. Therefore, the species composing the target material can be analyzed by inspecting a frequency of the absorbed radiant light. The frequency (c) is represented by an equation of c=&ngr;/&lgr;. In this equation, &ngr; represents a transferring velocity of a wave having a constant period and &lgr; represents a wavelength. An IR spectrum is illustrated by means of a wave number that is a reciprocal number of the wavelength.
In order to measure a concentration of each material included in a sample, a peak area at a peak region illustrated by each material in the IR spectrum is utilized. That is, the concentration of each material included in the sample may be noted by a relative size of the peak area illustrated by each material.
However, since a diameter of a measuring beam of the instrument is about 10 mm or larger, the beam is reflected and scattered by patterns formed on a substrate when the measurement is carried out on a BPSG layer formed on a semiconductor substrate. A distortion of the peak area due to the patterns is even more severe as a thickness of the BPSG layer increases.
In order to measure a concentration of a dopant in a BPSG layer during a semiconductor processing, a test sample is used. The test sample is obtained by forming a BPSG layer on a bare substrate using the same conditions as in the manufacturing process of the device. Then, the thickness and the concentration of the dopant are measured for the test sample and those of the BPSG layer are calculated using the measured result.
The test sample is formed considering various parameters to maintain the same state with a BPSG layer formed during actual semiconductor processing. However, when the sample is thick or when the intensity of the dopants in the sample is large, the intensity of the light transmitting the sample is insufficient so that detecting the transmitted light is difficult. In this case, the absorption intensity distribution is not illustrated clearly and a large numbers of split peaks are illustrated as noise around a main peak representing a specific material. Accordingly, the peak area cannot be calculated to precisely determine a concentration deviation. Thus, obtained data are unreliable.
In addition, a defect test and a concentration measurement for each processing step should be separately implemented, which increases overall processing time. Further, an additional process of forming the test sample must be implemented for every step of forming the BPSG layer during the semiconductor processing thereby increasing a manufacturing cost of the semiconductor device.
SUMMARY OF THE INVENTION
A first feature of the present invention is to provide a method of measuring concentration of a dopant using an infrared measurement, thereby obtaining reliable data even when an intensity of a transmitted light is small.
A second feature of the present invention is to provide a method of measuring concentration of a dopant using an infrared measurement, by which reliable data can be obtained even when an intensity of the transmitted light is very small thereby providing an unclear spectrum for some materials.
A third feature of the present invention is to provide a method of measuring concentration of a dopant of a semiconductor device, which can be repeatedly performed every time an insulation layer, including a dopant, is formed.
A fourth feature of the present invention is to provide a method of measuring concentration of a dopant of a semiconductor device, which can be applied along with actual semiconductor processing.
In accordance with a first aspect of the present invention, there is provided a method of measuring a concentration of a material including irradiating an infrared light onto a semiconductor substrate having a layer formed thereon, the layer including a first material and a plurality of dopants of which an entire intensity is less than an intensity of the first material, wherein a portion of the infrared light is absorbed in the semiconductor substrate including the layer and a remaining portion of the infrared light is transmitted through the semiconductor substrate including the layer; computing intensities of the infrared light absorbed in the first material and the plurality of dopants in accordance with light wave numbers by utilizing a difference between an
Choi Jeong-Hyun
Choi Sun-Yong
Jun Chung-Sam
Kim Kwang-Soo
Kim Tae-Kyoung
Lee & Sterba, P.C.
Niebling John F.
Samsung Electronics Co,. Ltd.
Stevenson Andre′ C.
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