Method and arrangement for determining the layer-thickness and the substrate temperature during coating

• US 5,564,830 A
• Filed: 01/18/1994
• Issued: 10/15/1996
• Est. Priority Date: 06/03/1993
• Status: Expired due to Term

• Current Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Original Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Inventors: Bauer, Norbert, Bobel, Friedrich
• Primary Examiner(s): GUTIERREZ, DIEGO F
• Application Number:
  US08/183,176
• Time in Patent Office: 1,001 Days
• Field of Search: 374/126, 374/7, 374/9, 374/130, 374/142, 364/557, 437/8, 356/381, 356/382, 356/445
• US Class Current: 374/126
• CPC Class Codes: G01B 11/0633 using one or more discrete wavelengths
• CPC Class Codes: G01J 2001/4242 Modulated light, e.g. for synchronizing source and detector circuit
• CPC Class Codes: G01J 2005/0074 having separate detection of emissivity
• CPC Class Codes: G01J 5/0003 for sensing the radiant heat transfer of samples, e.g. emittance meter
• CPC Class Codes: G01J 5/0007 of wafers or semiconductor substrates, e.g. using Rapid Thermal Processing
• CPC Class Codes: G01J 5/0804 Shutters
• CPC Class Codes: G01J 5/0805 Means for chopping radiation
• CPC Class Codes: G01J 5/80 Calibration using comparison with reference sources G01J5/52

Abstract

The invention describes a procedure and an arrangement for measurement of temperature and thickness of layer during a deposition or coating process. As coating or depositing processes known technologies of semi-conductor manufacturing arrangements, plasma devices, ion devices, and other dry-etching arrangements may be used. The invention can also be applied to the manufacture of optical coatings. As a consequence of interference of the thermal radiation of the substrate at the growing layer, the emissivity ε changes continuously during coating or depositing, therefore, a pyrometric measurement of temperature may not be applied. This basic problem is solved by the invention, which uses a reflectometer, which determines the reflectivity R of the wafer. According to the law of conservation of energy ε=1-R so that with said reflectometer the actual emissivity of the whole (multi-layer) system may be determined. The measurement of temperature then is effected by means of a determination equation. Concurrently the thickness is determined by a comparison of the reflectometer-curve and a theoretical dependency of thickness of layer.

Claims

1. A method for determining a thickness of a layer and a temperature of a substrate during deposition or coating of the substrate in arrangements for the manufacture of semi-conductors or in deposition-devices by use of a detected temperature radiation from the substrate when being coated, characterized in that:

(a) the emissivity (ε

) of the substrate being coated is determined according to equation;

space="preserve" listing-type="equation">ε

=1-R

in which;

ε

represents the determined emissivity Of the substrate being coated, and R represents the reflectivity determined by measuring the reflected radiation of the substrate being coated by reflectometry;

(b) the temperature (T) of the substrate is determined according to equation;

##EQU8## in which;

T represents the determined temperature of the substrate being coated,

T₀ represents the initial temperature of the substrate measured by pyrometry at the beginning of the deposition or coating,

P₀ represents the initial thermal radiation of the substrate measured by pyrometry at the beginning of the deposition or coating,

P represents the thermal radiation of the substrate being coated measured by pyrometry,

R₀ represents the initial reflectivity of the substrate before being coated measured by reflectometry,

L₀ represents the initial intensity of the reflected radiation of the substrate measured by reflectometry at the beginning of the deposition or coating,

L represents the intensity of the reflected radiation of the substrate being coated measured by reflectometry,

c₁ and c₂ each independently represent constants,

λ

represents the wavelength of incident radiation comprising mono-chromatic light on the substrate being coated from a light source, and

f_Planck (λ

, T₀) represents Planck'"'"'s radiation formula as a function of wavelength and initial measured temperature of the substrate; and

,

(c) the thickness (d) of the layer deposited or coated on the substrate is determined by comparing a measured reflectivity, determined by measuring the reflected radiation of the substrate by reflectometry, with a given reflectivity vs. layer-thickness dependence (R=f(d)).

2. The method according to claim 1, characterized in that:

(a) the thermal radiation of the substrate (P, P₀) is measured in a thermal radiation branch (B) which comprises a first detector for measuring thermal radiation of the substrate, and the reflected radiation by the substrate (R, R₀) of the source of radiation comprising mono-chromatic light is measured in a reflected radiation branch (A) which comprises a second detector for measuring reflected radiation of the light source by the substrate;

(b) phase-sensitive modulation means is provided with each detector, respectively, in which each phase-sensitive modulation means comprises a chopper and a lock-in-amplifier coupled therewith;

(c) in which said phase-sensitive modulation means provides that in one detector-branch (A) only the reflected radiation of the source of light, being reflected radiation from the substrate, is measured proportionally to reflectivity (R) and in said other detector-branch (B) only thermal radiation is measured proportionally to ε

.f_Planck ; and

,

(d) further in which said detectors are coupled to a digital signal processing means or analog processing means, being operative to determine the temperature (T) of the substrate from the detector signals in real time, applying the temperature (T) determination equation.

3. The method according to claim 1, characterized in that:

(a) the light of the light source is provided by the chopper in branch (A) in a first frequency region around f₁ corresponding to the reflected radiation and the lock-in-amplifier only registers around f₁, thereby filtering out thermal radiation frequency components and providing an output signal which is proportional to the reflectivity (R);

(b) the thermal radiation is modulated by the chopper in branch (B) in a second frequency region around f₂ corresponding to the thermal radiation and the lock-in-amplifier only registers around f₂, thereby filtering out reflected radiation frequency components and providing an output signal which is proportional to ε

.f_Planck.

4. The method according to claim 1, characterized in that:

(a) the determined temperature (T) is used for controlling a process for deposition or coating of substrates in the manufacture of semi-conductors.

5. The method according to claim 1, characterized in that:

(a) the substrate is a semi-conductor wafer.

6. An apparatus for determining a thickness of a layer and a temperature of a substrate during deposition or coating of the substrate in arrangements for the manufacture of semi-conductors or in deposition-devices by use of a detected temperature radiation from the substrate when being coated, comprising:

(a) a first detector for measuring the intensity of the thermal radiation of a substrate in a pyrometer-branch (B);

(b) a second detector for detecting reflected radiation, radiated from a source of light and reflected from the substrate in a reflectometer-branch (A);

(c) at least one filter for mono-chromatizing the source of light of the reflectometer-branch (A) and the thermal radiation of the substrate; and

,

(d) in which the first detector is provided with a chopper as well as with a lock-in-amplifier and the second detector is correspondingly provided with a chopper as well as with a lock-in-amplifier.

7. The apparatus according to claim 6, characterized in that:

the angle of incidence of the light of the reflectometer branch (A) and the angle of monitoring of the pyrometer branch (B) are substantially equal.

8. The apparatus according to claim 6, characterized in that:

said source of light comprises mono-chromatic sources selected from the group consisting of lasers, white-light sources, global bar sources (SiC), black-body-radiators, and halogen-lamps.

9. The apparatus according to claim 6, characterized in that:

both detector-branches (A;

B) are spaced apart from said light-source, when said radiation is incident on the substrate in a non-perpendicular way.