Process for forming a film composed of a nitride of a diffusion barrier material

A process for forming a refractory metal silicide stack with a nitride of a diffusion barrier material formed as a cover layer for the refractory metal silicide stack, the process comprising:

• depositing a layer of a refractory metal on a production silicon surface layer with physical vapor deposition in physical vapor deposition chamber having an environment containing gaseous nitrogen, said production silicon surface layer being situated on a semiconductor substrate;
• annealing the layer of the refractory metal in an environment containing gaseous nitrogen to form a layer of a silicide of the refractory metal;
• depositing multiple layers of the diffusion barrier material on a test silicon surface layer with physical vapor deposition in a physical vapor deposition chamber having an environment of varying gaseous nitrogen content;
• calculating and plotting the physical vapor deposition rate of the diffusion barrier material as a function of the varying gaseous nitrogen content, thereby producing a curve of the physical vapor deposition rate of the diffusion barrier material as a function of the gaseous nitrogen content, the curve having the shape of an outward pointing elbow, the elbow comprising a first continuous section of the curve with a downward slope, the first continuous section being connected at a point of transition to a second continuous section of the curve with a steeper downward slope, the point of transition comprising an optimum gaseous nitrogen content operating level that causes nitride nuclei of the diffusion barrier material to be uniformly dispersed throughout the sputter layer of the diffusion barrier material and that allows substantially no grain growth of a nitride of the diffusion barrier material in the layer of the diffusion barrier material while sputtering the layer of the diffusion barrier material on the test silicon surface layer;
• sputtering a layer of the diffusion barrier material over the layer of the silicide of the refractory metal in an environment comprising approximately 15 percent of the optimum gaseous nitrogen content operating level, wherein the diffusion barrier material is composed of a material selected from a group consisting of tungsten alloys of Group III and Group IV early transition metals, and Mo alloys of Group III and Group IV early transition metals;
• and
• growing nitride grains of the diffusion barrier material in the layer of the diffusion barrier material in an environment containing nitrogen to form a layer of a nitride of the diffusion barrier material, wherein the nitride grains of the diffusion barrier material of equal in size.

A process for forming a refractory metal silicide stack with a nitride of a diffusion barrier material formed as a cover layer for the refractory metal silicide stack, the process comprising:

• depositing multiple layers of the diffusion barrier material on a test polysilicon surface layer with physical vapor deposition in a physical vapor deposition chamber having an environment of varying gaseous nitrogen content;
• calculating and plotting the physical vapor deposition rate of diffusion barrier material as a function of the varying gaseous nitrogen content;
• producing a curve of the physical vapor deposition rate of the diffusion barrier material as a function of gaseous nitrogen content that has a first continuous section with a downward slope that is connected at a point of transition to a second continuous section with a steeper downward slope, the point of transition representing an optimum gaseous nitrogen content operating level that causes the nitride nuclei of the diffusion barrier material to be uniformly dispersed throughout a sputtered layer of the diffusion barrier material and that allows substantially no grain growth of a nitride of the diffusion barrier material layer in the sputtering layer of the diffusion barrier material during said sputtering of the layer of the diffusion barrier material onto the test polysilicon surface layer;
• and
• selecting a production gaseous nitrogen content to correspond to within approximately three percent of the optimum gaseous nitrogen content operating level;
• forming a nitridation on a polysilicon surface layer located on a semiconductor substrate by implanting nitrogen into the polysilicon surface layer;
• depositing a layer of a refractory metal on a production polysilicon surface layer with physical vapor deposition in a physical vapor deposition chamber having an environment of a carrier gas and gaseous nitrogen;
• annealing the layer of the refractory metal in an environment of gaseous nitrogen to form a layer of a suicide of the refractory metal;
• depositing a layer of the diffusion barrier material on the layer of the silicide of the refractory metal with physical vapor deposition within the physical vapor deposition chamber in the environment comprising an inert gas and said production gaseous nitrogen content, wherein there is between about 4×108 to about 4×1015 nitride nuclei of the diffusion barrier material per cm2 of the diffusion barrier material, wherein the diffusion barrier material is composed of a material selected from a group consisting of tungsten alloys of Group III and Group IV early transition metals, and Mo alloys of Group III and Group IV early transition metals;
• and
• growing nitride grains of the diffusion barrier material in the layer of the diffusion barrier material in an environment of gaseous nitrogen at a temperature of between about 400° C. and 700° C. to form a layer of a nitride of the diffusion barrier material.

A nitride formation process comprising:

• depositing multiple layers of a material including a refractory metal on a test substrate with physical vapor deposition in a physical vapor deposition chamber having an environment of varying gaseous nitrogen content;
• calculating and plotting the physical vapor deposition rate of the material including the refractory metal as a function of the varying gaseous nitrogen content, thereby producing a curve of physical vapor deposition rate of the refractory metal as a function of gaseous nitrogen content, said curve having a first continuous section with a negative slope, said first continuous section being connected at a point of transition to a second continuous section having a greater negative slope, wherein the point of transition comprises an optimum gaseous nitrogen content operating level;
• sputtering a target of said material including said refractory metal on a substrate without growing nitride grains therein in an environment of said optimum gaseous nitrogen content to form a layer of said material including said refractory metal having a uniform distribution therein of nitride nuclei, wherein substantially no nitride grains of said refractory metal grow during said sputtering;
• and
• heating the layer of the material including the refractory metal to grow therein nitride grains of said refractory metal, wherein the nitride grains of said refractory metal grow at the same speed and have the same size.

A method of making a metal nitride film, the method comprising:

• sputtering a target of a metal in an environment of multiple gaseous nitrogen content percentages to form, for each said gaseous nitrogen content percentage, a test layer of a nitride of said metal;
• plotting, for each said gaseous nitrogen content percentage, the deposition rate of each said test layer to produce a curve having a first negative slope, a greater second negative slope, and a transition portion therebetween;
• and
• sputtering, in an environment having a gaseous nitrogen content percentage corresponding to the transition portion, a target of said metal to form a final layer of said metal having therein nitride nuclei of said metal, wherein substantially no grains of the nitride of the metal grow during said sputtering.